DIFFERENCES IN TOWNSENDS CHIPMUNK POPULATIONS BETWEEN 2ND-GROWTH AND OLD-GROWTH FORESTS IN WESTERN OREGON

Because Townsend's chipmunks (Tomias townsendii) may be important in m aintaining natural ecosystem processes in forests in the central Orego n Cascade Range, we compared their population characteristics in young second-growth and old-growth forests. We live-trapped Townsend's chip munks in 5 young (30-60 yr old) second-growth and 5 old-growth (>400 y r old) Douglas-fir (Pseudotsuga menziesii) stands during spring and au tumn 1987-90 in western Oregon. We tested the null hypothesis of no di fference in characteristics of chipmunk populations in these 2 stand a ge-classes. Densities ranged from 0.4 to 10.3 chipmunks/ha and were gr eater (P < 0.05) in old-growth (xBAR +/- SE, 5.1 +/- 0.4) than in seco nd-growth (2.8 +/-0.3) stands. Chipmunk densities were related to larg e (greater-than-or-equal-to 50 cm diam at breast height [dbh]) snags i n old-growth (P = 0.002) but not in second-growth (P = 0.6) stands. Ch ipmunks in old-growth stands moved shorter (P = 0.03) distances in aut umn and had a greater proportion of young-of-the-year (P = 0.007) than those in second-growth stands. These differences suggest that old-gro wth stands provide better habitat for Townsend's chipmunks than young second-growth stands, and may reflect important functional differences in food chains and energy flow between the different stand age-classe s.